The present invention relates to methods for adding phosphate fertilizers to micro-irrigation systems, compositions used therein and stabilized micro-irrigation water.
The agriculture industry has developed the practice of adding plant nutrients to the plant environs, such as the soil, to enhance crop growth and subsequent yields. These fertilizers come in a variety of formulations depending on the specific crop to be grown and its nutrient requirements.
Fertilizers generally are classified according to their NPK content. NPK is common terminology used in the fertilizer industry and stands for: (1) N—the amount of nitrogen in the formulation as N; (2) P—the amount of phosphorus in the formulation as P2O5; and (3) K—the amount of potassium in the formulation as K2O.
Mankind learned to add these fertilizers centuries ago to grow better crops to feed the ever-increasing population. Initially, these materials were typical inorganic compounds that were mined by the local natives and simply added to the soil in which the crop was grown. As the population increased further, irrigation of the land to improve crops and crop yields became another common agricultural practice. Fertilization methods ultimately were facilitated by the practice of adding inorganic fertilizers to the water being used to irrigate the crops. The term “fertigation” is sometimes used for this combination of irrigation and fertilization. Although the early techniques were extremely crude by today's standards, the techniques nonetheless obtained better yields and drastically minimized the labor of applying these fertilizers.
Today's high demand for crops (food crops and otherwise) has turned agriculture into a technically-sophisticated business, and a business in which large corporate farms dominate the small family farm. The technical challenges faced by the modern agricultural industry include both the ever-increasing need for arable land, especially in the western and southwestern United States, and the decreasing availability and increasing cost of water. To meet the need for water conservation, today's technology includes micro-irrigation systems that deliver very precise amounts of water directly to the plant that is being grown. In the past 20 to 30 years a large percentage of crop producers in the western and southwestern United States have converted to irrigation systems utilizing this micro-irrigation technology.
Similar to the advent of “fertigation” practices generally, upon conversion to micro-irrigation systems, modern farmers began adding fertilizers to them. In micro-irrigation systems, unfortunately, water quality and the inclusion of fertilizers cause severe problems. The problems arise from a number of factors. (1) The most common sources of agricultural irrigation water, including micro-irrigation water, are reservoirs, lakes, ponds, canals, streams, rivers, wells, and water recycled from other uses, and combinations thereof, which waters contain various amounts of dissolved minerals. (2) Phosphate fertilizers can form insoluble salts and/or cause particulate formation when added to the irrigation water. Macro-irrigation systems mainly tolerate these conditions, while micro-irrigation systems are extremely intolerant.
The sensitivity of micro-irrigation systems to water quality and additives stems from the refinement of the components in a micro-irrigation system. In order to add precise amounts of water directly to the plant or crop being irrigated, micro-irrigation systems contain devices called emitters, micro-sprinklers or other such devices. These devices deliver the desired precise amounts of water so long as they do not plug or foul. Plugging occurs when deposits, from any source, build up inside these devices. The smallest particle or foreign material can cause fouling of these devices, because these devices have very tiny orifices and/or a long tortuous narrow passageway that provide the requisite pressure for delivery of precise amounts of water in a uniform manner to each plant in the crop being irrigated.
The addition of phosphate fertilizers to the micro-irrigation water increases the loading of inorganic salts over that already in the water. When the loading, or the combined loading, is too high, the solubilities of at least some of the naturally-occurring minerals and/or added compounds are exceeded and particulate formation increases dramatically. When particulates form, significant deposits begin to build up throughout the entire micro-irrigation system. The end result is plugging of the emitters or micro-sprinklers. Plugging results in uneven distribution of water and nutrients to the crop being irrigated. In some cases, complete shut-down of the irrigation system occurs. Therefore problem-free use of phosphate fertilizers in micro-irrigation systems is conventionally limited to the systems that use relatively pure water sources. When the water source is not sufficiently pure, the fertilizer is often distributed to the crop by means other than through the irrigation system, with the loss of “fertigation” benefits.